Hydraulic machines having a rotating group are generally known. One such machine is disclosed in U.S. Pat. No. 4,991,492. The rotating group of the hydraulic machine includes a shaft and a cylinder barrel that is connected to the shaft with a joint (or tripod) assembly. Pistons attached to the shaft extend into cylinder bores located in the cylinder barrel. When the cylinder barrel is angled relative to the shaft, the pistons move reciprocally within the cylinder bores. The cylinder barrel is tiltable relative to the shaft so that the hydraulic machine is capable of operating as both a hydraulic pump and a hydraulic motor.
In known hydraulic machines, like the one described above, the rotating group is submerged in hydraulic fluid for lubrication and cooling of the rotating group. Typically, the rotating group rotates at high speeds, at times up to 5,000 revolutions per minute. The rotation of the rotating group in the hydraulic fluid results in losses due to, amongst other things, flow resistance of the hydraulic fluid.
In order to reduce these losses, it is desirable to provide a hydraulic machine in which the rotating group is not submerged in hydraulic fluid. To accomplish this, some lubrication should be provided to locations of relative movement of the joint assembly with the shaft and cylinder barrel. The high speed of rotation of the rotating group makes such lubrication difficult as centrifugal force tends to force any lubricating fluid to the exterior of the rotating group.